FROM THIS EPISODE

Major American companies are changing their strategies when it comes to global warming. We hear about the political consequences of Exxon Mobil and others now being willing to pay tax on carbon emissions, amid growing concern about the urgency of preparing for climate change. Also, Nelson Mandela's life is honored in a Soweto stadium, and GM chooses the first woman to lead an American auto-maker.

Nelson Mandela, who died last week at age 95, was memorialized by a massive crowd today in Soweto, South Africa. President Obama, one of many heads of state who took part in today's four-hour service, received a long ovation from tens of thousands crowded into an open stadium in pouring rain. Sudarsan Raghavan was there for the Washington Post.

Four years ago, the fossil-fuel lobby helped to beat back President Obama's proposed cap-and-trade system to reduce greenhouse emissions. Exxon Mobil, America's most profitable company, led the way in global warming denial. Times have changed and Exxon Mobil is beginning to sound more like Al Gore. The oil giant would even be willing to pay a tax on carbon emissions. Other oil companies would too, along with Walmart, DuPont and General Electric. They're now in direct opposition to former Republican and Tea Party allies, at a time of warnings that climate disasters could be "sudden and unexpected." Would a carbon tax help to slow global warming? What would it mean for company profits and the cost of living?

Earlier this week, the US government sold its last shares of General Motors. Today, the company named the first female to head a major American car company. Earlier this year, GM's chairman and CEO, Dan Akerson, told a women's business group in Detroit that what he called a "car gal" would soon head one of the Big Three. Now, he's stepping down early, to be replaced as CEO by Mary Barra. Daniel Howes is a columnist for the Detroit News.